At least one witness told investigators that Pickens, a student at Texas Christian University, took the prescription drug Xanax and later injected heroin in the hours before he died, the sources said.

Pickens was pronounced dead Tuesday morning at Baylor All Saints Medical Center, where a friend brought him after saying he wouldn't wake up. He already may have been dead for several hours, the sources added.

Pickens had been staying at an off-campus condo, Fort Worth police Cpl. Tracey Knight said. The Tarrant County Medical Examiner will determine his cause of death, she added.

A young man who answered the door at the condo did not want to give his name, but said that he and his cousin -- also TCU students -- were with Pickens on Monday night.

The man, who was visibly shaking, said Pickens told them he had taken Xanax earlier Monday and later used heroin inside their condo when the two had gone to the store and left Pickens alone.

When they returned from the store, Pickens appeared to be sleeping, he said.

Tuesday morning, when Pickens did not wake up, he and his cousin carried his body to a car, he said. His cousin drove Pickens to the hospital while he went to class, he said.

The man said police searched the condo for drugs later Tuesday morning, but he could not say what officers found.

Police had not yet decided late Tuesday whether or not to arrest anyone who may have been involved in the alleged drug use.

Knight said homicide detectives were notified of the death but it wasn't known if they would lead the investigation.

News of the death and the possible drug connection was certain to spread fast across the TCU campus following a well-publicized drug raid just last year.

A spokesman for Pickens' grandfather issued a written statement:

"Ty’s loss at such a young age is an unspeakable family tragedy for the entire Pickens family and his many friends. We mourn his passing and respectfully request that the family be allowed to grieve in private in this time of sorrow," said Jay Rosser, spokesperson for T. Boone Pickens.

The university also emailed a statement.

“We are deeply saddened by the loss of this member of our community and our hearts and thoughts are with Ty’s family at this time,” said Cavins Tull, TCU vice chancellor for student affairs. “Staff members are available if students need to speak with someone about this sad news.”